Paving mixture



Patented June 7, 1932 their STATES PATENT FFICE I JAMES EDGAR BLACK, OF KANSAS CITY, MISSOURI, ASSIGNOR TO NATIONAL PAVE- MENTS, INCORPORATED, OF KANSAS CITY, MISSOURI, A CORPORATION OF ARIZONA.

PAVING MIXTURE No Drawing. Application filed March 28, 1929. Serial No; 350,821.

This invention relates to improvements in been found in actual tests that the fine clayey paving mixtures and process of making the same, and refers more particularly to paving mixtures known in the trade as the cold mix 5 type. I

The invention is an improvement on my Patent No. 1,596,232, issued August 17, 1926, and a patent issued to M. A. Popkess, No.

material has a particular afiinity for the asphaltic substance, more or less freeing the solvent or diluent for evaporation.

As a solvent or cut back material any light c;

oils or similar fluids are contemplated, such as petroleum dlstillates including gas oil gasoline, naphtha kerosene and related distillates, ethers, naphthas or other light, easily vo'latilized liquids which will combine with the binder to thin it. 'Such cut back liquid does not Wet the clay grains but enters between them and prevents cohesion or plasticity of the clay grains giving workability to the mass while the asphalt in the binder is being absorbed by the clay grains. After such action the light volatiles of the binder are largely released and quickly evaporated from the. mixture after it has been laid an rolled. Among the solvents that have been used effectively are various petroleum and coal tar distillates having the ability to volatilize at atmospheric temperatures. The cut back materials, after having combined with the 1,320,709, on November 4:, 1919. H The present invention consists of a paving mixture composed of coarse aggregate such as rock, gravel and/or sand and a fine aggregate such as an earthy or clayey material incorporated and intimately mixed with a lt water-proof building material such as cut back asphalt. The materials are combined without heat and are laid and rolled while cold. 7 Among the important advantages of such mixture are the elimination of expensive heating and mixing asphalt plants, the cost of heating and re-handling the aggregates and asphalt in preparing them for the actual I -laying operation. I Heretofore difiiculties have been en'- countered in the preparation of cold paving mixtures utilizing a cut back asphalt binder in the incorporatlon of sufficient fine aggreasphalt and mixed with the coarse aggregate and fine clayey material while cold, produce a uniform mix with the fines evenly distributed with the binder over the coarse aggregate, while the out back material is in a condition in which it will easily and quickly evaporate from the mixture.

The mixture when laid gives an increased tensile strength to the pavement as compared with cold mixtures which do not contain the fine clayey material.

In preparation, the asphaltic binder is mixed with the cut back material which dilutes it to a relatively fluid liquid. This is then combined with thecoarse and fine clayey material in a pug mill or other suitable apparatus which will assurean intimate combination of the ingredients. The character of the stone aggregate and the relative percentp; ages of the coarse aggregate and the fine clayey material depend more or less upon the purpose to which the mix is intended. For a thin coating or surfacing the aggregate may be smaller than in the case of thick paving work. In a typical case the percentage ;-gate to give a proper density to the pavement, because the cut back asphalt mixture would be sealed up and evaporation retarded, leaving the pavement in a poorly cemented condition.

In the present invention these diificulties have been overcome by adding to the mineral aggregate a clayey material oran earthy mineral aggregate comprising a substantial percentage of the mixture and consisting of discrete particles or fines which material may be used in the preparation of hot mix.

The clay material used as a filler in preparing the cold mix herein mentioned is the same as that described in my previous Patent, No. 1,596,232, issued Aug. 17, 1926. This 45 clayey mineral aggregate not only serves as a filler and gives density to the pavement, but combines with the asphalt in such a manner that the rolled surface is sufficiently porous to permit the escape or liberation of 50 the volatiles used with the binder. It has 1'39 of asphaltic cement or binder is approximately 4 to 6 per cent.

Due to the even distribution of the asphalt by the solvent material through the aggregates, it has been found that the amount of asphaltic binder may be reduced With relation to the amount of asphaltic Waterproofing material" used in connection With a hot mix of a similar character.

This type of pavement also permits the use of a relatively Wide range of asplialts, as the fine clayey material When bonded With the asphalt-ic material prevents its Working to the surface under trailic and producing a slippery pavement. A typical mix of the material using an asphalt produced from petroleum is shown beloW.

Cut back asphalt adaptable for use in mixtures' of this character should have a specific viscosity at 122 F. of from 10 to 100. The amount of cut back asphalt for such a mixture Will be from 4% to 10% of the total mix.

Coarse aggregate included for use in the present cold mixture will range from material which will pass a 1 4 inch mesh screen down to fines.

'lypical mixture Per cent Passing a 1 4 screen and retained on a screen 35 Passing a screen and retained on a screen 25 Passing a 1A)" screen and retained on a ,3" screcn Q0 Passingn 10 mesh screen (preferably river sand) 10. 5 Clay dust 5 Cut hack asphalt a 4. 5

The analysis of other mixtures Which have given satisfactory results are as follows:

Percent Per cent Cut back asphalt 4 Clay dust all passing 50 Passing 1 screen and retained on -33 screen 25 3G Passing-% screen and retained on a 2 mesh screen 530 Passing a 2 mesh screen and retained on a 4 mesh screen 30 125 Passing a 4 mesh screen and retained on a 10 mesh screen 35 Ductility at 77 F... 100- Solubility in carbon disulphide 99. 84%

Although typical examples have. been shown of the mixtures as Well as the cut back binder material, itis understood that these disclosures are not added to limit the inventionto such materials or proportions of material but-merely to showcertain operable and feasible examples.

A range of materials adapted to be used is disclosed and-variations in theproportions and character of the aggregate and fines are contemplated.

The binder material will vary according to the location of the Work and the conditions to which the pavement is to be subjected.

I claim as my invention:

1. A paving mixture adapted to be laid cold, consisting of a relatively coarse mineral aggregate, substantially equal proportions of a cutback asphaltic binder and a discrete clay material suliiciently fluid to be mixed Without heating, the latter having an adsorptive attraction for the asphalt.

2. A paving mixture adapted to be laid cold, consisting of a relatively coarse mineral aggregate, substantially equal proportions of an asphaltic binder cut back with a diluent vehicle in sufiicient quantity to be mixed cold,

and a discrete clay or earthy material having I an adsorptive attraction for the asphalt in the hinder, the binder having a specific viscosity at 122 F. of from 10 to 100.

3. A paving mixture adapted to be mixed and laid cold, consisting of 60% to 85% of relatively coarse mineral aggregate, 4 to 10% of an asphaltic binder cut back with a diluent vehicle, 5 to 10% of discrete clay material having an adsorptive attraction for the asphalt.

4. Apaving mixture adapted to be mixed and laid cold consisting of a relatively coarse mineral aggregate and an asphaltic binder cut back With a diluent vehicle and a discrete earthy or clay material, the binder and clay proportioned in the mix in substantially the relation of 4 to 6.

5. A paving mixture adapted to be mixed and laid cold consisting of a coarse aggregate, a discrete clay or earthy material and an asphaltic binder cut back With a diluent vehicle, the proportion of clay relative to the asphaltic binder present being in substantially the relation of 4 to 6, and the mixture and asphalt and clay comprising from 7% to 20%.

6. A paving mixture adapted to be mixed and laid cold, composed of 60 per cent to 85 per cent of relatively coarse aggregate of mineral matter, 15 to 25 per cent or" relatively finer aggregate of mineral matter, 4 to 9 per cent of an asphaltic cement made liquid by a diluent vehicle, 5 to 10 per cent of discrete clay having an adsorptive attraction for the asphalt in the liquid cement.

JAMES EDGAR. BLACK. 

